The isolation, detection and subsequent analysis of nucleic acids play a central role in molecular biology, and may be used, inter alia, as a starting material for diagnosis and prognosis of diseases and disorders. The recent discovery of trace amounts of short, fragmented nucleic acid in a range of biological samples, including plasma and serum, presents a new opportunity for improved, non-invasive tests. Previously, the recovery of fragmented nucleic acid from biological samples was considered unimportant, and extraction methods were designed to isolate large, undegraded nucleic acid. However, it is short base pair nucleic acid (e.g., highly degraded RNA and DNA) that offers a new source of highly informative genetic material for a wide range of applications, including prenatal diagnostics, early cancer detection and the study of apoptotic DNA from host and non-host sources.